1. Field of the Invention
The present invention relates to an active power supply with power factor correction and output voltage regulation, which especially means a device that can achieve power factor correction by drawing low THD (total harmonic distortion) and non-pulsating current from municipal power supply (alternating current and precisely regulate the output voltage.
2. Description of the Prior Art
Traditional interactive uninterrupted power supply (UPS) that has a voltage stabilizer to regulate the voltage is shown in FIG. 1. This kind of interactive UPS is also called single conversion UPS. When compared to relatively traditional ON-Line UPS, it has the advantage of using fewer components, so its reliability and efficiency is higher. Nevertheless, its disadvantage is no power factor correction for input power. Therefore, when the UPS is subject to a nonlinear load, it fails to meet the harmonic wave current regulation, such as IEC1000-3-2. Besides, the interactive UPS also can cause stepwise voltage fluctuations and imprecise voltage control. Please refer to FIG. 2, which is related to U.S. Pat. No. 5,334,877 and applicable to the interactive UPS. Although the patent describes a method that is capable of power factor correction, it still fails to perform precise regulation on output voltage.
Accordingly, the above-mentioned device still has many disadvantages and needs further improvement.
In view of the disadvantages for the traditional device, the inventor is eager to seek improvement and innovation. After many years of research and development, the inventor finally accomplished the present invention of an active backup power supply with power factor correction and output voltage regulation.
It is the objective of the present invention to provide an active backup power supply with power factor correction and output voltage regulation, which not only improves THD and regulates output voltage, but also harmonic wave current. Thus, both input current and the size of electromagnetic component are minimized.
Another objective of the present invention is to provide an active backup power supply with power factor correction and output voltage regulation, which improves the traditional device over the stepwise voltage fluctuation and imprecise voltage regulation.
The active backup power supply with power factor correction and output voltage correction to achieve the above-mentioned objectives comprises: a power factor correction circuit (PFC), an inverter with two outputs, a backup battery and a control circuit. The power factor correction circuit connects to AC power source (municipal power supply) to draw low THD current, which flows through the first output of an inverter and then goes to the load via the second output. For the municipal power supply, current with PFC is dependent on input power, which is equivalent to the real power required by the load. The second output of the inverter connects to the output of UPS. The first output of the inverter is controlled by PFC to be higher than the municipal input voltage. So PFC can operate in voltage boost mode and draw non-pulsating current. Meanwhile, the inverter is controlled by PFC to generate a fixed voltage source. Besides, the fixed voltage source from the inverter and the current source from PFC are parallel connected to provide power to the load. When the load is resistive or linear, its current is fully supplied by PFC and there is almost no current flowing through the inverter. When the inverter is non-linear, it will draw distorted current and the current difference between load demand and PFC supply will flow through the inverter. Since the inverter is a power source of low resistance in nature and its current can cause very minimal voltage distortion, stable and regulated output voltage can be generated.